Video compression

Video compression technologies are about reducing and removing redundant video data so that a digital video file can be effectively sent over a network and stored on computer disks. With efficient compression techniques, a significant reduction in file size can be achieved with little or no adverse effect on the visual quality.

There are three different video compression standards: Motion JPEG, MPEG-4 and H.264. H.264 is the latest and most efficient video compression standard.

Motion JPEG or M-JPEG is a digital video sequence that is made up of a series of individual JPEG images. When 16 image frames or more are shown per second, the viewer perceives motion video. Full motion video is perceived at 30 (NTSC) or 25 (PAL) frames per second.One of the advantages of Motion JPEG is that each image in a video sequence can have the same guaranteed quality that is determined by the compression level chosen for the network camera or video encoder. The higher the compression level, the lower the file size and image quality. The main disadvantage of Motion JPEG is that it makes no use of any video compression techniques to reduce the data since it is a series of still, complete images. The result is that it has a relatively high bit rate or low compression ratio for the delivered quality compared with video compression standards such as MPEG-4 and H.264.

MPEG-4 supports low-bandwidth applications and applications that require high quality images, no limitations in frame rate and with virtually unlimited bandwidth.

H.264 is the latest MPEG standard for video encoding. H.264 is expected to become the video standard of choice in the coming years. This is because an H.264 encoder can, without compromising image quality, reduce the size of a digital video file by more than 80% compared with the Motion JPEG format and as much as 50% more than with the MPEG-4 standard. This means that much less network bandwidth and storage space are required for a video file. Or seen another way, much higher video quality can be achieved for a given bit rate.

In the video surveillance industry, H.264 will most likely find the quickest traction in applications where there are demands for high frame rates and high resolution, such as in the surveillance of highways, airports and casinos, where the use of 30/25 (NTSC/PAL) frames per second is the norm. This is where the economies of reduced bandwidth and storage needs will deliver the biggest savings.

H.264 is also expected to accelerate the adoption of megapixel cameras since the highly efficient compression technology can reduce the large file sizes and bit rates generated without compromising image quality. While H.264 provides savings in network bandwidth and storage costs, it will require higher performance network cameras and monitoring stations.